It is often desirable to coat substrates with protective and/or decorative films resulting from the application and/or curing of various compositions. Such protective and/or decorative films may be thermoplastic or thermoset films, and may be uncured, partially cured or completely cured. Illustrative compositions include paints, coatings, primers, varnishes, adhesives, sealants, lacquers, polymers and the like. Illustrative substrates include metal substrates, plastic substrates, natural substrates such as wood, stone, concrete, and the like, as well as combinations thereof. In many instances, it is mandatory that the film strongly adhere to the substrate, typically by one or more of a chemical, mechanical, and/or covalent bonding mechanism.
However, while strongly adherent films are typically required, it is often necessary at some point to remove a previously applied film from a substrate. Removal may be desirable either before or after the applied film has been completely cured and may occur either sooner or longer after application to a substrate. In the case of the removal of a completely cured film from a substrate, it is often necessary to break or damage a three-dimensional cross-linked matrix.
Compositions used to remove films from substrates are known in the industry and are often referred to as paint removers, paint strippers, paint removing compositions, paint stripping compositions, and the like, and are collectively referred to herein as ‘film removing compositions’. Film removing compositions commonly used in the industry have traditionally included ‘active ingredients’ such as methylene chloride (MCL), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), phenols, acids, caustics, and combinations of one or more of such materials. Unfortunately, these known ‘active ingredients’ have been associated with certain disadvantages.
For example, although MCL containing compositions are a common and cost-effective film removing composition from a material standpoint, they are undesirable given the fact that MCL is volatile and regulated by state and/or federal agencies. Concerns have also been raised with respect to the toxicity, safety and ease of handling of materials such as MCL, phenols, caustics and acids. Materials such as caustics and acids can also attack the underlying substrate during the film removal process and result in undesirable substrate damage. Materials such as DMSO and NMP have been known to show inadequate efficacy at ambient conditions and are sometimes subject to regulatory and reporting requirements. Finally, film removal compositions containing one or more of these ‘active ingredients’ have been known to exhibit limited stability over time.
Thus, film removing compositions are disadvantageous when they are associated with one or more concerns relating to safety, toxicity, volatility, handling, substrate damage, efficiency, cost, stability, and the like. Numerous attempts to address and minimize such concerns have been made by the prior art.
For example, U.S. Pat. No. 3,954,648 discloses liquid compositions for removing coatings from coated metal surfaces. The liquid compositions are comprised of from one-fourth to about 10% by weight of an alkali metal hydroxide, from 40 to about 60% by weight of at least one high boiling oxygenated solvent and from 40 to about 60% by weight of at least one high boiling amine.
U.S. Pat. No. 4,508,634 discloses compositions suitable for removing paint, grease, dirt, and other foreign materials from the skin. The compositions comprise propylene carbonate, water, at least one organic cosolvent that can be an ester of an aliphatic monobasic or dibasic acid, at least one thickening agent, at least one neutralizing agent, and at least one surfactant.
U.S. Pat. No. 4,594,111 discloses a liquid phase cleaner-solvent consisting essentially of from about 50% to about 90% by weight of water, less than 10% by weight of sodium chloride, from about ½ to 1% to about 10% by weight of coconut amide, from about ½ of 1% to about 8% by weight of a tall oil fatty acid, from about 1% to about 15% by weight of isopropyl alcohol and from about 5% to about 40% by weight of propylene carbonate and a process for removing oxidation from metal surfaces using the liquid phase cleaner-solvent.
U.S. Pat. No. 4,927,556 discloses a composition for removing coatings from surfaces consisting essentially of at least one dibasic ester, water, and at least one thickening agent.
U.S. Pat. No. 4,956,115 discloses aqueous stripper compositions comprising water, trioxane, a surfactant and optionally a mixture of cosolvents comprising an aliphatic alcohol, an ester of an aliphatic carboxylic acid and an aromatic hydrocarbon or minimally hetero-substituted derivative thereof. The amount of the organic cosolvent is limited to about 30 wt. % to provide a stripper composition that is less volatile and more biodegradable than conventional stripper compositions.
U.S. Pat. No. 5,106,525 discloses water-soluble coating remover compositions comprising γ-butyrolactone, an organic acid, and water, and optionally include solvents, surfactants, thickeners, and rust inhibitors. The coating removers of the invention are said to be uniquely effective in that they are both water rinse able and capable of removing highly crosslinked coatings.
U.S. Pat. No. 5,215,675 discloses water-soluble stripping compositions containing a solution of water, a water soluble ester containing from 4 to 10 carbon atoms and an amount of hydrogen peroxide or compounds which generate hydrogen peroxide in situ; which peroxide concentration is not in excess of 30 wt. % of the water/ester composition.
U.S. Pat. No. 6,348,107 discloses a paint stripper for use by immersion of a painted substrate in a bath of the composition or application in place that has two phases, one aqueous and the other of partially water soluble organic solvent. The aqueous phase is saturated with organic solvent. The organic solvent is preferably benzyl alcohol, a dibasic ester or ethyl-e-ethoxypropionate; the total amount of organic solvent in the bath is suitably in the range of 2 to 20%.
U.S. Patent Application Publication No. U.S. 2002/0198124 discloses methods and compositions for the removal of coatings such as paint from surfaces. The disclosed methods are typically conducted between about 45° and about 75° C., and the compositions typically contain a carbonate, a dibasic ester, a pyrrolidine and a monoester.
It can be seen that attempts by the prior art to provide improved film removing compositions have not been wholly successful. It would therefore be desirable to provide a film removing composition that is free of one or more of concerns relating to safety, toxicity, volatility, handling, substrate damage, efficiency, cost, stability, and the like. It would be particularly desirable to provide a film removing composition that is associated with reduced concern in several of these areas. It would be especially desirable to provide an aqueous film removing composition that exhibits one or more improvements in volatility, toxicity, substrate damage, safety and handling, but is also advantageous with respect to stability, cost, and effectiveness.